The process commonly used commercially for the production of the economically most important monomeric alkoxysilane, tetraethoxysilane, involves two main steps. The first of these entails the synthesis of silicon tetrachloride. This can be made in a variety of ways. In one, silica (sand) is reduced to elemental silicon with carbon in an electric arc furnace, and this is then chlorinated with elemental chlorine. The reduction of the silica to silicon consumes large amounts of electrical energy, a fact reflected in the cost of the silicon. Once the silicon tetrachloride has been prepared, it is reacted with ethanol to produce the tetraethoxysilane: EQU SiCl.sub.4 +4C.sub.2 H.sub.5 OH.fwdarw.Si(OC.sub.2 H.sub.5).sub.4 +4HCl
An economically important alkoxysiloxane is made by the hydrolysis of tetraethoxysilane. It contains 40 wt % SiO.sub.2 and is often called ethyl silicate 40.
Various alkoxysilanes are made by a transesterification process: ##STR1## Among the catalysts used for this process are sodium alkoxides. This process is used mainly for the preparation of the alkoxysilanes of alcohols with relatively high boiling points.
The process currently most widely used commercially to make alkyl silicones, and particularly methyl silicones, is over forty years old. It is generally known as the direct process. The first step involves the reduction of silica (sand) to elemental silicon in an electric arc furnace. This step consumes large amounts of electrical energy, a fact reflected in the price of silicon produced by this process. The second step involves the oxidation of silicon with methyl chloride in the presence of a copper catalyst. This step produces (CH.sub.3).sub.2 SiCl.sub.2 and a multitude of other products including CH.sub.3 SiCl.sub.3. In general, this step is conducted so as to maximize the production of (CH.sub.3).sub.2 SiCl.sub.2, which is then separated from the other products by distillation. This separation requires careful control of conditions because (CH.sub.3).sub.2 SiCl.sub.2 and CH.sub.3 SiCl.sub.3 have boiling points which differ by only 4.degree. C. and, because, in general, high purity (CH.sub.3).sub.2 SiCl.sub.2 is required for the next step in the process. Due account must also be taken of the corrosive and toxic nature of many of the species produced in this step. Once the pure methylchlorosilanes are isolated, they are hydrolyzed to form silicones: EQU n(CH.sub.3).sub.2 SiCl.sub.2 +nH.sub.2 O.fwdarw.[(CH.sub.3).sub.2 SiO].sub.n +2nHCl
The resulting mixture is then either separated by distillation or rearranged in the presence of an acid or a base catalyst to give the desired products.
In molecular terms, the direct process involves three steps. The first leads to displacement of all the oxygen atoms on the silicon, the second leads to methylation of the silicon atoms, and the third leads to the attachment of some oxygen atoms on the silicon atoms and to the formation of the desired silicon-oxygen backbone.
Two other processes are also important in the synthesis of silicones. In one, HSiCl.sub.3 is produced by the reaction of silicon with HCl or by other means. The HSiCl.sub.3 is then catalytically added to olefins: ##STR2## The resulting organochlorosilanes are used directly or are converted into silicones.
In the second of these processes chlorosilanes are treated with organometallic reagents: EQU SiCl.sub.4 +2RMgX.fwdarw.R.sub.2 SiCl.sub.2 +2MgXCl
Again the resulting organochlorosilanes, after being separated, are used directly or are converted to silicones.
The latter two processes are used primarily for the production of silicones in which some of the organic groups are other than methyl groups. It is apparent that these two processes and the direct process all have undesirable features.
In other work related to the field of the present invention, Compton and Petraitis (U.S. Pat. No. 4,309,557) describe the preparation of organosiloxanes by the treatment of organoalkoxydisiloxanes and organoalkoxytrisiloxanes with Grignard reagents. This work shows that organosiloxanes can be made from such precursors, and suggests that organosiloxanes can be made from siloxane compounds containing only alkoxy groups. Calhoun and Masson (J.C.S. Dalton 1980, 1282) found that hexaisopropoxycyclotrisiloxane is formed as a very minor byproduct when pseudowollastonite, Ca.sub.3 Si.sub.3 O.sub.9, is treated with trimethylchlorosilane, hexamethyldisiloxane, and isopropyl alcohol. This work shows that alkoxysiloxanes can be made from silicates as byproducts under the reaction conditions used by the authors.
Further, it should be noted that Bleiman and Mercier (Inorg. Chem. 1975, 14, 2853) found that the sheet silicate chrysotile, Mg.sub.3 Si.sub.2 O.sub.5 (OH).sub.4, (common asbestos) can be partially converted to a partially esterified sheet silicate by treating it with hydrochloric acid and isopropyl alcohol and then treating the resulting material with allyl alcohol and pyridine.